1edk
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(New page: 200px<br /><applet load="1edk" size="450" color="white" frame="true" align="right" spinBox="true" caption="1edk" /> '''STAPHYLOCOCCAL PROTEIN A E-DOMAIN (-60), NMR...)
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Revision as of 11:48, 20 November 2007
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STAPHYLOCOCCAL PROTEIN A E-DOMAIN (-60), NMR, MINIMIZED AVERAGE STRUCTURE
Overview
The E-domain of staphylococcal protein A is one of five homologous, IgG-binding domains designated E, D, A, B, and C that comprise the, extracellular portion of protein A. The E-domain binds tightly to Fc, fragments of IgG and binds certain Fv fragments with micromolar affinity., To explore further the structural features of Fc binding by protein A, and, as a first step in developing a structural understanding of E-domain/Fv, complex formation, we have determined the solution structure of the, uncomplexed E-domain using 2D homonuclear and heteronuclear NMR, spectroscopy. Complete 1H and 15N resonance assignments were obtained, and, the structure was determined from 383 NOE-derived distance restrains, 34, phi and 19 chi 1 dihedral angle restraints, and 54 restraints for 27, H-bonds. 3JH alpha-H beta coupling constants and long-range NOEs involving, Phe11 indicate the side chain exists in more than one conformation with, differing chi 1 values. NOE restraints that were incompatible with chi 1 =, -60 degrees were removed from one set of structure calculations, and those, incompatible with chi 1 = 180 degrees were removed from a second set to, allow Phe11 to explore both rotamer wells. Thus, two sets of 20 final, structures, having no distance or dihedral angle restraint violations, greater than 0.12 A or 1.6 degrees, respectively, represent the solution, structure of the E-domain. Backbone atomic rms differences with respect to, the mean coordinates for each set of 20 structures for residues 8-53, averaged 0.41 +/- 0.06 and 0.35 +/- 0.06 A. No significant differences in, the overall structure result from the different orientations of Phe11. The, solution structure of the E-domain consists of three alpha-helices that, pack together to form a compact helical bundle. A detailed comparison, between the E-domain ensembles and the previously determined structure for, the B-domain in complex with Fc indicates that only the 180 degrees chi 1, rotamer of Phe11 is competent for binding; the -60 degrees chi 1 rotamer, must reorient to 180 degrees to create a cavity that is filled by Ile253, from the CH2 domain of Fc in the Fc-bound complex.
About this Structure
1EDK is a Single protein structure of sequence from Staphylococcus aureus. Full crystallographic information is available from OCA.
Reference
Solution structure of the E-domain of staphylococcal protein A., Starovasnik MA, Skelton NJ, O'Connell MP, Kelley RF, Reilly D, Fairbrother WJ, Biochemistry. 1996 Dec 3;35(48):15558-69. PMID:8952510
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